PREFACE: Three outstanding examples from the Armstrong Siddeley range of engines form the subject-matter of the present volume. The engines in question are: the "Cheetah IX," the " Tiger VIII," and the " Lynx IVC." Each section begins by describing briefly the leading features of the engine under discussion. Detailed instructions are then given for the dismantling, inspection, and re-assembling of the component parts. Broadly speaking, each section deals with what may be described " top overhaul," and particular attention has been given to the correct use of tools which have been designed to facilitate the work on the various engines. Wherever possible the detailed description of methods to be adopted has been supplemented by perspective drawings. It has been found by experience that graphic illustrations of this type can often be used to convey practical information much more effectively than pages of descriptive text. We believe that every reader will appreciate the advantage of these illustrations. We are especially indebted to the Armstrong Siddeley Company for their invaluable assistance in the compilation of this section. Whilst every care has been taken to ensure that the information given is up to date, it will be realised that minor improvements and modifications are continually being made in aero engines which are in such extensive use in military and civil aircraft.